DEAR DOCTOR K:
My son has amblyopia. Can we “force” him to use his bad eye?
Amblyopia is a condition in growing children in which one eye doesn’t see as well as the other. Remarkably, the brain figures out which eye is seeing properly and begins to ignore information from the bad eye. (There’s a video illustration of how this works at the end of this post.)
The brain’s action helps the child in the short run: The child stops seeing double from a crossed eye, for example. But if the brain ignores the signals from the bad eye for too long, then even if the problem — the crossed eye, or a cataract — is fixed, the brain still will ignore that eye. This can lead to a lifelong loss of vision in the weaker eye. That’s why recognizing the problem and fixing it as soon as possible is critically important. Amblyopia may result from:
Crossed eyes. A crossed eye does not move properly. If a child needs to look to the right — because her mother is calling, for example — one eye may not move fully to the right. The child has double vision — two images of the mother, one to the right of the other. To prevent this confusing image, a child may focus the good eye more than the eye that doesn’t move properly.
Severe nearsightedness or farsightedness. If one eye is more severely affected than the other, the brain may ignore images from the weaker eye.
Structural problems.Vision may be blocked by a structural problem of the eye or eyelid. One such problem is a cataract, a part of the lens of the eye that, instead of being crystal clear, starts to get cloudy. This blocks light from reaching the back of the eye. Although cataracts normally occur in older people, children can be born with them. Treatment aims to produce clear vision in both eyes. Depending on the cause of your child’s bad eye, treatment may involve:
- Prescription eyeglasses to correct focusing problems.
- Surgery and eye muscle exercises to realign crossed eyes.
- Surgery to correct any structural problem.
The second treatment goal is to strengthen the weak eye. Your child will wear a patch over his stronger eye for several hours each day (“forcing” him to use his weak eye). Patching typically continues for at least six months. Some ophthalmologists use an opaque contact lens in place of a patch. Others prescribe eye drops that temporarily blur vision in the stronger eye. Until recently, doctors believed that amblyopia couldn’t be successfully treated after mid- to late childhood. However, new evidence suggests that vision may be improved with prompt, appropriate treatment regardless of the age at which amblyopia is diagnosed. It’s still best to begin treatment early. Proper treatment during early childhood often produces near-normal vision in the affected eye. ambylopia_anim_15
Video credit: National Eye Institute, National Institutes of Health